Stock Banana SR71 Attributes? - Page 3 - RC Groups
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Aug 03, 2009, 08:53 AM
On the Edge of Space
dLdV's Avatar
For sure, rudders would be slick, the thing would be an eye popper in knife edge. Keep us posted if you like.

This one is all sorted out, everyday flier type now. Next, it'll be the donor for an ME-262 power system transplant, and get an upgrade to 5400Kv on 55mm fans with 4S 4500mAH. That's a month or so on, though.

Catch ya later.
Last edited by dLdV; Sep 05, 2009 at 08:26 PM.
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Aug 08, 2009, 12:14 PM
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I'm still awaiting some free time to sort the details of the damage out.
Aug 11, 2009, 07:02 PM
Registered User
Originally Posted by dLdV
Good score on the F-16. I paid $40 more for the Kyosho 55mm Falcon, 60cm/24in. span, receiver ready . The plane flies nicely though, very stable, smooth and predictable. Foolishly low passes, not a real barn burner but not slow either. The tailerons barely move on that one. Not bad for such a small plane. First EDF for me, though I had some pusher jet experience. Blackbird is EDF #2.

Took some measurements of control surface deflections. Thanks for the suggestion, I need a starting reference too, still tinkering with setup. The measurements are distance rather than angle due to too lazy to devise an appropriate method of measuring. Could measure elevon width and Pythagoros it, but too lazy for that too. Sticking to single rate due to don't know any better.

The static reference point is the top surface of the rearmost and outermost part of the wing. The dynamic reference is the center of the rearmost point of the elevons.

+5mm up with controls neutral, both surfaces

+15mm up / 0mm down full right stick or full left stick. Most of the movement is when the stick is well over to the side, I'm using positive expo, which should dampen the response near neutral stick if I'm understanding the ing DX6i manual.

+27mm full up stick

-20mm full down stick

I still find it twitchy on roll axis in crosswind, considering dialing in more expo. It seems to need a lot of up in turns at times, I think its because our field is only W=150 meters X L<=300 meters, dimensions courtesy of Google Maps. Subtract from the width parking, the flight line, and keeping the plane a few meters in front of you - the plane has to turn about in 120 meters or so. It likes to drop the nose a good deal in certain conditions. Its not hard to deal with, it just wants a buttload of up.

The inlet cones are in storage til winter. The grass keeps snatching em out. The grass was mowed 2 days before this pic, before that it had been a month. So til autumn, its very little with wheels, nothing with odd protrusions.

Hope to hear more flight reports. Its interesting to compare notes, e.g. after much tinkering and figgering, this settled out to pretty much the same power system as your stock version.

Finally, (sigh of relief from the audience) after reading way too many posts about this airplane, roll axis seems to be a factor in a lot of crashes.

"Never Mind The "
S. Vicious
Influential English Philosopher, circa 1980
Not sure what you mean on ailerons travel. '+15mm up / 0mm down full right stick or full left stick." No down ward deflection of ailerons on opposite side?
Aug 11, 2009, 10:51 PM
On the Edge of Space
dLdV's Avatar

New Control Throw Measurements

All Hail the Originator!

Hey Stuka, we commandeered your thread, it seemed like a good place to compare notes. D, we finally have some company! These measurements are current and are influenced by the rate and expo settings, which are posted on the previous page. The thing is flying OK now, as easy or easier than its other squadron mates. I'm using the mix method for DX6i found here post#35 -

CG is 78mm back from the front lip of the nacelles
Bonus Measurement - Lever Arm Lengths:
Servo arm screw center to clevis pin - 12mm
Bottom surface of elevator to clevis pin - 13mm

The static reference is still the top surface of the rear and outermost tip of the wing, dynamic reference the point at the very back of the elevator. (Example: Top of the wing tip 60mm above bench, rear tip of taileron 65mm above bench... 65-60 =+5mm). Trims are centered.

Neutral stick: +5mm
Full Up stick: +27mm
Full down stick: -15mm
Full L/R stick: +15/-8mm

Probably best to match the 5mm up deflection carefully, the rest ballpark is probably OK. Can't guarantee results, but mine is flying very controllably over 15 flights or so, and I'm a so so pilot sober.

Not sure what you mean on ailerons travel. '+15mm up / 0mm down full right stick or full left stick." No down ward deflection of ailerons on opposite side?
At the time of that earlier batch of measurements, that is what it was, not sure how or why. Mechanical differential? Did something odd in Tx setup?

PS This is weird, but after launch you might need a little up trim
Last edited by dLdV; Aug 17, 2009 at 11:56 AM.
Aug 12, 2009, 09:25 AM
Registered User
Thanks for the update and info. I want to maiden this before the snow flies and will have to hand launch. After two years still cant find suitable surface locally to ROG. As to the hijack, have fun guys. I actually forgot the thread after the original post. Golf you know.
Aug 15, 2009, 03:05 PM
Registered User
I maidened my SR71 last weekend. Couldn't get off the ground on the first attempt so I added a few degrees of up sub trim for the second attempt. After a fairly long run (on tarmac) she lifted off and I flew a couple of circuits adding further up trim all the time to keep her level. I then reduced power to land and immediatly she dived almost vertical. In the short space of time I had before the inevitable crash I discovered there was no responce to the elevators so I applied full power again. She levelled just before hitting the ground, the u/c taking the full force of the impact and was dissplaced somewhat rearward. Apart from that there was no other damage.
I have fitted two zippy 2200 lightpower lipos in parrallel in the battery bax which was moved about 2 inches back. The Cof G worked out to be 16mm forward from the specified position of 78mm back from the front of the nacell which I considered at the time wouldn't make a great deal to the control response. At the moment I am blaming this forward CofG for what happened.
Have any of you fellows found the CofG position critical with this bird?
Aug 16, 2009, 06:39 AM
On the Edge of Space
dLdV's Avatar
I think the 78mm CofG works well for pitch stability. Mine is flying ok balanced there. Cutting throttle results in a smooth transition to glide with no sudden pitch down, provided the flying speed is adequate. On the other hand, if the plane is flying very slowly and power is cut, the nose may pitch up, so land well before the ESC hits low voltage cutoff.
Last edited by dLdV; Aug 17, 2009 at 11:33 AM.
Aug 16, 2009, 07:22 AM
Registered User
Thanks dLdV.
I have got the CoG at 78mm now so am now ready to fly again but it won't be for a week or so, heading for the hills today to spend a few days flying my 28% scale ASW20. The SR71 should provide a large contrast in flying style to that of the ASW!
Aug 17, 2009, 10:48 AM
On the Edge of Space
dLdV's Avatar
Hope all goes well. I'd be very interested to hear how it turns out. This is my favorite model, it isn't the fastest or anything else, it's just a sight to behold when aloft. Its incredible how modern that airframe still looks despite the fact it was probably on the drawing board in the late 1950's or so.
Sep 05, 2009, 08:35 PM
On the Edge of Space
dLdV's Avatar
Well, the operation was a success. The 4300Kv 64mm 2.2AH 3S setup is out, 5400 55mm 4AH 4S in. It's much heavier but it seems faster. The first flight it flew for a while but somehow got into a flat spin. Not sure if a motor quit or I flew it into the spin. Anyway, it helicoptered to the ground with little damage, like a maple seed. Freaky. The second flight was uneventful.

Anyone got any war stories to relate on this plane? I guess this thread is about dead, the Blackbird is so four months ago, uck uck uck .
Last edited by dLdV; Sep 05, 2009 at 09:02 PM.
Sep 07, 2009, 07:39 PM
Registered User

SR 1 Flight.

Well, Did not have good luck with my first SR flight today. First attempt ended up in the SR just bouncing down the runway with full up elevator" did not have enough to maintain level flight. Made sure I was at 78 mm and gave myself more elevator throw.

2nd attempt lifted off but pitch and roll was touchy; also had a good cross wind to deal with. She bounce again but this time broke her back and right wing on the 2nd hit. Its fixable but man this thing seemed unstable; I must have something way off.

Are you guys flying 3 or 4 S?

3S it seemed like the motors were not producing the power needed. I have Easy Tigers Version of the SR and he says that you can also fly on 4S?
Sep 07, 2009, 07:58 PM
On the Edge of Space
dLdV's Avatar
I've had 3 different power setups in the same airframe. I got mine airframe only. Brief descriptions:

1) 3600Kv 64mm fanmotors, 3S 2.2AH 30C batt., 20A ESC's. Take off from grass - no way. Hand launch - easy. Just barely flew on a little under 300W. Speed maybe 30 mpH. Control - no problem, used gyros on roll and pitch. Took off landing gear because hand launch and belly flops were no problem. It probably would have flown fine on 4S, but the speeders and motors were both limited to 3S. It liked to pitch the nose up and stall in this configuration. DO NOT try this setup. it's absolute minimum power required.

2) 4300Kv 64mm fanmotors, 3S 2.2AH 30C batt., 40A ESC's. Take off from grass - don't know, no gear. Hand launch - easy. Flew about 50 or 60 mpH estimated on about 580W. Control - Took off gyros after a few flights. It was slow on pitch and crazy twitchy on roll. Eventually got it tamed out with dual rate and expo settings (see post #34), it was easy to fly. It was pretty much an everyday flier, but it would have been tough to get it settled out without the computer radio. Batt.s got a little hot, 2.6 or 2.8AH probably would have been OK. Shockwave, If you have 3600 or 3800Kv motors I suspect it would be about like this setup on 4S, as long as all the hardware is harmonized to take the power.

3) 5400Kv 55mm fanmotors, 4S 4.0AH 30C batt., 60A ESC's. Hand launch is still easy. Pretty fast at almost 1000W. Handles OK, but likes to rock the wings. I wrecked it into the woods today, just plain lost my bearings, but this'll be wreck recovery #5 or so, no sweat. I have my Master Foamsmith Certificate. (apologies to whoever I ripped off the word "Foamsmith" from).

Thanks for posting.
Last edited by dLdV; Sep 12, 2009 at 01:46 PM.
Sep 07, 2009, 08:10 PM
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Joe 1320's Avatar
Originally Posted by ShockWave

Are you guys flying 3 or 4 S?

3S it seemed like the motors were not producing the power needed. I have Easy Tigers Version of the SR and he says that you can also fly on 4S?
Hard to take anything he says seriously.

I fly mine of 4s with 4000 kV don's wicked motors. Then again, it's pretty sick power. If he says it flies on 4s then try it. If it burns up something, he should replace it..... as you went on his word as a vender.
Sep 08, 2009, 07:14 AM
On the Edge of Space
dLdV's Avatar
Let's go guys, need more war stories, the good the bad and the ugly. Hints, tips, suggestions, bragging, rants, outright fish stories - whatever. How's your Bird?

BTW, went to ETM and the model description is pretty clear, the power system is supposed to handle 4S no problem. Go for it, Shockwave.
Last edited by dLdV; Sep 08, 2009 at 07:46 AM. Reason: exercise 1st Amendment right to say whatever I want no matter how idiotic
Sep 08, 2009, 09:10 AM
Registered User
Concerning CG:
I am flying with the CG at 90mm back from the front lip of the nacelles.
78mm does not work. I do not have have enough sub trim to keep the plane leveled.
90mm works fine with an elevon sub trim of 5mm.

Last edited by micbu; Sep 10, 2009 at 02:42 AM.